The overall objective of this study is to determine the biochemical mechanism by which polypeptide hormones, such as adrenocorticotropic hormone (ACTH) regulate gene expression. The focus is to determine how ACTH stimulates the expression of the P-450-17-alpha (CYP17) gene, which codes for the 172-hydroxylase/17, 20-lyase enzyme of steroid hormone biosynthesis. ACTH stimulates an increase in CYP17 gene expression in humans, cows and rabbits, but not in rats, as judged by a lack of increase, in enzyme activity. The structure of the human and bovine genes have been determined. determining which of the nucleotide sequences of the 5'- and other regulatory regions of CYP17 are conserved in rabbit, cow and human, but altered in rat, may provide insight to possible sequences required for ACTH stimulation of transcription and gene expression. Subsequent construction and expression of chimeric genes consisting of the suspected regulatory sequence and a reporter gene, such as chloramphenicol acetyl transferase, will allow functional evaluation of the putative regulatory sequence(s). Several congenital deficiencies of steroidogenic enzymes exist. 172-Hydroxylase deficiency can result in infertility, hypertension, or secondary sexual abnormalities. These deficiencies could be due to mutations in the structural or regulatory elements of the gene. Thus, determination of the DNA structure necessary for regulation of this gene has medical importance.